1. Field
The invention is in the field of vacuum cleaners that operate on compressed air.
2. State of the Art
Vacuum cleaners that operate on compressed air are known, see for example U.S. Pat. Nos. 2,863,525 and 5,142,730. Such vacuum cleaners operate from a source of compressed air such as available in many factories and garages. Electrical connection is unnecessary and the risk of electrical sparking is eliminated. Further, such vacuum cleaners can produce high air flow and, as opposed to most electrical vacuums, the vacuum produced is increased as the flow of air into the vacuum is reduced. Such vacuums have been found particularly useful in industrial applications for liquid spill pickup. The inventor has found that such vacuums are particularly useful in automobile repair stations and shops where spills of oil, transmission fluid, antifreeze, gasoline, water, etc., occur during auto and truck repair.
The vacuum cleaners of the indicated patents include canisters that fill up with dirt or liquid. The canister of U.S. Pat. No. 2,863,525 has a hinged bottom that can be opened to empty the canister while U.S. Pat. No. 5,142,730 says that the canister can be emptied, but no way of emptying it is shown or described.
Several models of compressed air vacuum cleaners are manufactured and sold by IAS Industrial Vacuums of Cornelius, N.C. These vacuums use canisters, such as fifteen to fifty five gallon drums, for collection of dirt or liquids picked up by the vacuum. It appears that these are emptied from the top by removing the vacuum generating apparatus, which is located over the open top of the drum. A model called the Sump-N-Ator sump vacuum, Model 2108, is designed to pick up liquid and then can pump the collected liquid from the drum. However, the liquid exits the top of the drum with a pipe extending toward the bottom portion of the drum to pick up the liquid, which allows solids to build up in the bottom of the drum. This vacuum cleaner includes a filter to filter and collect solid particles from the liquid entering the chamber. The filter keeps larger solid particles from building up on the bottom of the drum although sludge can still build up. Further, the filter has to be changed when filled.
None of the vacuum cleaners have a convenient system of emptying the canister and preventing build up of material on the bottom of the canister. Further, while some of these vacuum cleaners are supported on wheeled drum dollies, these can still be difficult to move around.